netdev - Re: [PATCH vhost v3 2/4] virtio_net: big mode skip the unmap check

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Message-ID: <1714012507.44893-1-xuanzhuo@linux.alibaba.com>
Date: Thu, 25 Apr 2024 10:35:07 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: virtualization@...ts.linux.dev,
 "Michael S. Tsirkin" <mst@...hat.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 netdev@...r.kernel.org
Subject: Re: [PATCH vhost v3 2/4] virtio_net: big mode skip the unmap check

On Thu, 25 Apr 2024 10:11:55 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Wed, Apr 24, 2024 at 4:17 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > The virtio-net big mode did not enable premapped mode,
> > so we did not need to check the unmap. And the subsequent
> > commit will remove the failover code for failing enable
> > premapped for merge and small mode. So we need to remove
> > the checking do_dma code in the big mode path.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >  drivers/net/virtio_net.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index c22d1118a133..16d84c95779c 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -820,7 +820,7 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
> >
> >         rq = &vi->rq[i];
> >
> > -       if (rq->do_dma)
> > +       if (!vi->big_packets || vi->mergeable_rx_bufs)
>
> This seems to be equivalent to
>
> if (!vi->big_packets)


If VIRTIO_NET_F_MRG_RXBUF and guest_gso are coexisting,
big_packets and mergeable_rx_bufs are all true.
!vi->big_packets only means the small.

Did I miss something?

Thanks.


>
>
> >                 virtnet_rq_unmap(rq, buf, 0);
> >
> >         virtnet_rq_free_buf(vi, rq, buf);
> > @@ -2128,7 +2128,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
> >                 }
> >         } else {
> >                 while (packets < budget &&
> > -                      (buf = virtnet_rq_get_buf(rq, &len, NULL)) != NULL) {
> > +                      (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> >                         receive_buf(vi, rq, buf, len, NULL, xdp_xmit, &stats);
> >                         packets++;
> >                 }
>
> Other part looks good.
>
> Thanks
>
> > --
> > 2.32.0.3.g01195cf9f
> >
>